File on desktop can not be deleted?

Finder says the item is being used by another task. try again when task is complete. There is nothing runnning and it has been on my desk top for weeks with several tries to delete it. ANy help would be greatly appreciated. Oh yea its a pdf.sit file and when I try to open it it says error has occured while expanding. Archive may contain damaged content. error #17538 but that doesn't matter anyways as I just want to delete it. Thanks in advance.
Dan

I'm not all too familiar with removing files via the terminal but I do understand that if you're not all too sure what you're doing you can do some serious damage. I think sometimes, while the advice is with good intention, is not very helpful when dealing with someone who's accustomed to a GUI.

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